1. Field of the Invention
This invention relates to marine devices that cut lines, nets, weeds and the like, and more particularly to shearing cutters that employ a blade rotating with the propeller of a vessel that cooperates with a non-rotating blade mounted on a non-rotating portion of a vessel adjacent the shaft.
2. Description of the Prior Art
Lines, nets, weeds and the like are commonly encountered by vessels. They may be swept by the propeller blades into the propeller shaft apparatus where they can cause great harm, i.e. into the space where the propeller shaft extends from its housing. There they may cut through the oil seals causing loss of lubricant. The current trend toward long line fishing wherein heavy monofilament nylon many miles long is lying in the water has exacerbated the problem. Applicant's U.S. Pat. No. 4,943,249, Jul. 24, 1990 teaches a unique means for adjusting the distance between a pair of radially extending shearing cutters, one of which is attached to a non-rotating portion of the ship and one of which is attached to a rotating portion of the ship.
The position of the propeller will change relative to the hull, advancing axially when under way in forward due to the forward thrust of the propeller. Heating and cooling of the shaft will also change propeller axial position. A sensing mechanism senses propeller location and a moving mechanism moves the non-rotating blade to accommodate these changes in relative propeller location to maintain a fixed, very close spacing between the two blades for effective shearing action.
U.S. Pat. Nos. 4,447,215; 4,507,091; 4,544,363 and 4,801,281 issued to Applicant disclose means for mounting both rotating and non-rotating shearing blades on the shaft so that axial shaft displacement has no effect on relative blade spacing. A simple, inexpensive mechanism for maintaining the correct distance between a rotating blade on a shaft or propeller and a non-rotating blade mounted on a non-rotating portion of the ship for optimum shearing action between the two blades despite axial movement of the shaft and propeller would be useful for many waterbome craft.
Applicant's U.S. Pat. No. 5,017,167 issued May 21, 1991 teaches a slot and slot follower mechanism for maintaining relative axial position between rotating and non-rotating parts of a line and weed cutter mechanism to compensate for axial movement of the propeller and shaft, with the slot rotating and the slot follower not rotating. Cutting lines and weeds free of the rotating shaft and propeller enhances propeller efficiency and prevents line from damaging the shaft seals. However, prolonged operation causes excessive wear between the slot and slot follower from constantly rubbing against each other. This alters the relative axial alignment between the parts leading to functional failure and requiring expensive replacement of large parts.